Structure of the Earth • Earth’s Interior is divided into 3 layers that have very different properties: • Crust • Mantle • Core • Our knowledge of these layers has come mainly from the study of earthquake waves.
The Crust • The crust is the outer-most layer of the Earth. • It is between 5 and 100 kilometers thick. • It is the thinnest of the Earth’s layers. • It is where we live.
The Crust • The crust is made up mostly of oxygen, silicon & aluminum. • There are two types of crust • Oceanic crust • Continental crust
Types of Crust • Oceanic crust is the crust that lies below the Earth’s oceans. • It consists mostly of basalt – a dark, dense igneous rock with a fine-grained texture. • Continental crust forms the continents and consists mostly of granite - a less dense igneous rock with larger crystals that is usually light in color.
The Mantle • It lies from about 40 to 2,900 kilometers below the surface. • The next layer after the crust is the mantle. • It is much thicker than the crust. • It contains about 67% of the Earth’s mass. • It is a layer of hot rock. • The mantle is denser than the crust. • It consists of a number of zones.
L I T H O S P H E R E • The crust and the uppermost part of the mantle are very similar. They are both rigid. Click for graphic • Together they are called the lithosphere. • Litho means “stone.” • The lithosphere is about 100 kilometers thick.
The Mantle • As you go deeper into the mantle, heat and pressure increase. • This makes the rock less rigid. • It has the consistency of tar and can bend much like plastic (semi molten). • This plastic-like layer of the mantle is called the asthenosphere. • The lithosphere floats on top of the asthenosphere. • Beneath the asthenosphere solid mantle material extends all the way to Earth’s core. • This lower solid part of the mantle is called the mesosphere.
The layer of the Earth that extends below the mantle to the center of the Earth is the core. The Core • The core makes up about 1/3 of the Earth’s mass. • It has two layers: • A liquid outer core • A solid inner core • Both are made of iron and nickel. • Despite enormous pressure, the molten metal of the outer core behaves like a thick liquid. • The inner core is a dense ball of solid metal. • The pressure is so great that the iron atoms cannot spread out and become a liquid.
Earth’s Magnetic Field • Currents in the liquid outer core cause the solid inner core to spin. • The inner core spins at a slightly faster rate than the rest of the planet. • This movement creates the Earth’s magnetic field, which causes the entire Earth to act like a giant bar magnet.
Review • The crust and the top, rigid part of the mantle make up the lithosphere. • The Earth is made of three basic layers. • The plastic-like layer of the mantle is called the asthenosphere. • The innermost rigid part of the mantle is called the mesosphere. • The core has two parts. • The outer core is liquid. • The inner core is solid.